Method of indirectly producing color photographs



Patented Apr. 24, 1934 UNITED STATES METHOD OF INDIRECTLY PRODUCING.

COLOR PHOTOGRAPHS Bela Gaspar, I Berlin, Germany No Drawing. ApplicationFebruary 9, 1931,

Serial 1930 22 Claims.

This invention relates to a method for the indirect production of colorphotographs.

It has already been proprosed ,for the indirect production of colorphotographs to add leuco-bases to a silver salt emulsion, and to convertthese into the particular color as a result of the interaction betweenthe silver reduced upon the development and the leuco-bases, whereby thelocally deposited quantity of silver in the developed picture determinesthe degree of color formation (including therefore the intensity of thecolor) for every point of the sensitized layer.

This method, however, has not been successful in view of the fact thatthe leuco-bases are very inconsistent, while the plates or papers arenot capable of being stored for any length of time in their unexposedstate, this also applying to the finished picture, as the resultingcolors very easily diffuse and the colors which it has been proposed toemploy are extremely unlasting, i. e. not fast.

According now to the invention, there are em-' ployed in place of theleuco bases the esters, ester salts or ethers of the leuco-compounds, orother equivalent colorless substances from which the dyes are derived.

In the process according to the invention silver salt emulsions will,generally speaking, also form the basis of operations, and for thisreason these will be primarily referred to in the followmg.

For the purpose of converting the ester, etc. into the correspondingcolors,'the silver deposit of the developed picture is first convertedinto a compound which will act on the ester, etc. This compound may havean oxidizing, condensing, reducing or saponifying action, in accordancewith the chemical nature of the color-form- 40 ing substance employed.

.According to a more recent invention, it is proposed with theassistance of esters or ester 'salts of the leuco-compounds to producecolorforming substances by thedirect method effected by light. In thiscase the leuco-substances take the part ofthe sensitized. substance,which part, inthe present invention, is assigned to the silver salt(orinore'generally speak to the semi -Jtized metallic salt). The newmethod with its subsequent conversion of the image, consisting of ametallic deposit, into a color image accordingly represents in face ofthe said direct method an indirect process. The invention covers areaction in the dark and the known direct method areaction underthaefiect of light.

In Germany March 1,

To more clearly explain the invention, various examples are quoted inthe followingf- In order, for example, to produce a blue pic- REISSU EDJUN 23 1940' ture diacetyl indigo white is incorporated in the silveremulsion and the sensitized layer is exposed, developed and fixed'in thecustomary v fashion. The leuco-substance in question is not sensitive tothe ordinary photographic baths employed, which condition, of course,requires to be observed not only in connection with the present example,but also in all other cases. The silver image produced is converted inthe known manner into one consisting of an oxidizing compound,preferably into a lead chromate image. This is immersed in an acidsolution, for example, a weak muriatic acid orsulphuric acid solution,whereupon the leuco-substance is converted into the desired color. Thesuperfluous leadsalt is thereupon removed, and the leucosubstance whichhas not been acted upon (at the unexposed or less exposed parts)treatedwith the known means (fixing salts and acetone).

The conversion of the leuco-substance into the dye represents in theexample above described an oxidizing and at the same time also asaponifying process. If as an equivalent color-forming substance thereis employed indoxyl sulphate of potassium or other salts of indoxylsulphuric acid or analogous compounds, for example thionaphthenic acid,.etc., iiidol or indol-carbonic acid and the lead chromate'image isimmersed in a hydroiodic acid solution, and thereupon in an alkalinesolution, indigo is again formed by oxidation and condensation. Ifdia'cetylindigotine is employed as color-forming substance, and thesilver image is converted into a ferrous iron salt image, indigo isformed by reduction.

may be made to the cinchonic salt of the sul- 9 phuric acid ester fromthe leuco-compound 616' dibrom dimethyl bis-thionaphthene-indigo. Thesilver developed from a layer containing this substance is converted inthe known manner into peroxide of manganese, and the layer thereupontreated in an acid solution, the red color forming thioindigo rose. Insimilar manner it is also possible to employ the esters of other dyes,for example, helindon yellow, tetrabromide indigo, etc. Ethers of theleuco-compoundof the dyes may also be employed, for example, ethyl etherof the hydrofiavanthrene.

An additional example of conversion of the ester salts into theparticular color at the points which have been subjected to exposure, orat certain points of the silver image resides in the following:-

The silver image is converted in the known manner intovanadyl-ferrocyanide, which acts as 5 oxygen carrier, or catalystrespectively, and is subsequently converted into the particular color ina weak sulphate solution of potassium bromate -or sodium chlorate. Ifdesired, the conversion of the silver image into a color image may beperformed with one single solution if the developed silver image istreated in a solution of certain oxidizing agents, for example potassiumchlorochromate (or potassium bicliromate muriatic acid) or in a dilutedpotassium bromate solution, which is weakly acidified'and contains asmall amount of iodine potassium. Suitable leuco-substances are, forexample, sulphate esters from the leuco-compounds of 6.6 dibrom dimethyl-bis thionaphthene indigo' and hexabrom-indigo. The use of these baths,or the conversion into the'particular color respectively, may also beperformed after the development and prior to the fixing.

The leuco-substances may also be converted into the particular colors atthe points which have not been exposed, i. e. at the points which arefree from metallic or silver deposit, by taking a diluted potassiumbichromate solution which has been weakly acidified with sulphuric acid,dissolving the silver image at first formed, and thus again developingthe remaining halogen silver and converting the silver image thus formedinto the particular colour. However, it is also possible to convert asilver image containing a leucosubstance into an inverse image in directfashion. In this connection a suitable leuco-substance will be found toexist, for example in sulphate ester of the leuco-compound oftetrabrom-indigo.

This is treated in a solution as follows:--.1 g.-

potassium bichromate, .1 g. sodium chlorate, 1 cubic centimetre 20%sulphuric acid and 50 cu. ems. water.

An additional possibility resides in the use of water-solubleleuco-compounds, for example sodium salts of sulphuric acid esters fromthe leuco-compounds of indigoidal dyes. These are subsequently depositedin the layer in the form of insoluble cinchonine salts, or mixed withcarrier colloids of that kind which greatly adsorb the salts, forexample gelatine, collodion or cellulose ester.

The sulphate esters of the leuco compounds of vat dyestufis have theproperty of impregnating the gelatine (for example the sodium salt ofsulphate ester'from the leucoeco'rnpound 'oi' hexabrom-indigo) so thatthe same cannot be re moved by washing, andmay' thereforeals'o beincorporated in the'gelatinewithout 'a fixing.

agent. The fixing is even better if at the same time there is added anorganic, acid, for example tartaric acid, or a tanning'agent,. such aschromium alum. The developer should be neutral as far as possible orresponsive to a weak acid. In

the present case the fixing agent requires to contain a substancaforexample sodium carbonate, responding to alkali. By utilizi g the saidprop-, erty of the sulphate ester the latter may be introduced into thelayer prior to or following exposure and development, the layer beingimmersed in a solution of this ester or ester salts, or the substanceapplied to or pressed into the same. In the latter case, it is alsopossible to apply several different colors, for example in the manner ofa screen, if necessary, mixed with filter colors and sensibilizers. Theconversion to the particular color occurs in the same manner asdescribed above.

Water-soluble leuco-substances may also be fixed at the exposed pointsof the image by tanning, whereupon the soluble leuco-substance at theunexposed or weaklyexposed points is removed, for example by acetone,and thereafter the leuco-compounds, which have been fixed by the tanningprocess, converted into the particular color by a sodium nitritesolution. The wellknown ferricyanide bichromate bath or also a tanningdeveloper may be employed for the tanning process.

The method in question is not confined merely to silver salt emulsions.It is, for example, quite possible to produce a picture composed ofmanganese or iron salts, in which case, of course, conversion of themetallic deposit into a compound capable of undergoing reaction isunnecessary.

According to the invention two or more color pictures may aso beproduced by super-imposing two or more layers, i. e. applying the layersone above the other, whichare each tuned to a certain character of light(wave-length limits) and t have the corresponding leuco-substanceincorporated therein. In addition to leuco-substances resulting inbrilliant colors it is also possible to add to the emulsionsleuco-substances providing a black or similar color on the lines offour-colour print. Use will naturally be made of correspondingsensibilizers and filter colors. Two different emulsions may be appliedto the front and rear side of a film respectively. Alternatively, two

or more different emulsions may be combined by re-emulsion. According tothis process at first complementary color negatives, or negativescontaining the correct colors but permutated black and white, areproduced, which may be copied on to a similar material, for example fromfilm on to film, or plate on to film, or plate and film on to paper. Itis, however, also possible to make copies on copying material preparedaccording to this process from any desired source, such as colordiapositive, color screen plate, color tracing. etc.

The process according to the invention also permits of combination withthe known photographic coloring processes, more particularly in thosecases in which the silver compound is converted into those chemicalsubstances which, in addition to the purpose of converting theleucocompounds into the particular color, are also adapted for fixingcolors or for tanning the gelatine, etc.v For example, the lead chromateac- 130 cording to the first example described in the above is convertedinto lead sulphate, whereby an oxidizi'ng process is caused by reason ofthe chromic, acid released, and thlead sulphate is coloured with a basicdye, for example fuchsin. This par- 135.

ticular method will be found to offer advantages for subsequentcorrection of the coloring.

It will be understood that no restriction is made to the specificexamples above referred to and that various modifications are quitepossible within the meaning of the description and the annexed claimswithout departing from the spirit of the invention.

What I claim as new and desire to secure by Letters Patent is:--

l. A method of producing colored photographic images, consisting inadding to a durable leuco compound in the preliminary stages of vatdyestuffs, from which the dyestuffs are derived; a sensitized metallicsalt emulsion, performing exdesired colo *7; A method of producing colorphotographic 9 images, cgnsisting massing a durable leuco corn-;-

pound to a sensitize .m tallicsalt emulsion, per-" posure, developingand fixing in the customary manner, and then introducing the exposed,developed and fixed image into a bath acting on the said compound andlocally converting the said compound into the colorat the desiredpoints.

2. A method of producing colored photographic images, consisting inadding esters of leuco compounds to a sensitized metallic salt emulsion,performing exposure, developing and fixing in the customary manner, andthen introducing the ex posed, developed and fixed image into a bathacting on the said compound and locally converting the said compoundinto the color at the de sired points.

3. A method of producing colored photographic images, consisting inadding ester salts of leuco compounds to a sensitized metallic saltemulsion, performing exposure, developing and fixing in the customarymanner, and then introducing the exposed, developed and fixed image intoa bath acting on the said compound and locally converting the saidcompound into the color at the desired points.

4. A method of producing colored photographic images, consisting inadding ethers of leuco compounds to a sensitized metallic salt emulsion,performing exposure, developing and fixing in the customary manner, andthen introducing the exposed, developed and fixed image into a bathacting on the said compound and locally converting the said compoundinto the color at the desired points.

5. A method of producing colored photographic images, consisting inadding to a durable leuco compound in thepreliminary stages of vatdyestuffs, from which the dyestuffs are derived; a sensitized metallicsalt emulsion, performing ex posure, developing and fixing in thecustomary manner, and then introducing the exposed, developed and fixedimage into a bath and converting the said image into a compound actingon the said leuco compound, thereby producing the color at the desiredpoints by interaction with the said leuco compound.

6. A method of producing colored photographic images, consisting inadding a durable leuco compound to a sensitized metallic salt emulsion,performing exposure, developing and fixing in the customary manner, andthen introducing the image into a bath and converting the exposed,developed and fixed metallic salt into a compound rich in oxygen, andliberating oxidizing agents at subsequent treatment, thereby producingthe y' 'oiiidation of the said leuco comforming exposure, developing andfixing in the customary manner, and then introducing theexposed,developed and fixed image into a bath rich in oxygen, thereby producingthe desired color by interaction between the said compound, the metallicdeposit and the said oxygeneous bath.

8. A method of producing colored photographic images, consisting inadding a durable leuco compound to a sensitized metallic salt emulsion,performing exposure, developing and fixing in the customary manner,introducing the exposed, developedand fixed image into a bath,converting the metal deposit into a condensing agent, and thenintroducing the said image into a second bath thereby producing thedesired color by condensation.

duigtionof the sensitizedemulsionand prior to 9. A method of producingcolored photographic images, consisting in adding a durable leucocompound to a sensitized metallic salt emulsion, performing exposure,developing and fixing in the customary manner, introducing the exposed,developed and fixed image into a bath, converting the metal deposit intoa reducing agent, and then introducing the said image into a second baththereby producing the desired color by reduction.

10. A method of producing. colored photographic images, consisting inadding a durable leuco compound to a sensitized metallic salt emulsion,performing exposure, developing and fixing in the customary manner,introducing the exposed, developed and fixed image into 'a bath, therebyconverting the metal deposit into a catalyzing agent, and thenintroducing the said image into a second bath thereby producing thedesired color by catalyzation.

11. A method of producing colored photographic images, consisting inadding a durable leuco compound to a sensitized metallic salt emulsion,performing exposure, developing and fixing in the customary manner,introducing the exposed, developed and fixed image into a bath acting onthe said compound and converting the said compound into the desiredcolor and subjecting the picture after the color formation to aphotographic toning process of the known kind.

12. A method of producing colored photographic images, according toclaim 1, consisting in adding the said leuco compound after productionof the sensitized emulsion and prior to development.

13. A method of producing colored photographic images, according toclaim 1, consisting in adding the said leuco compound after productionof the sensitized emulsion and following development.

14. A method of producing; {colored photographic images, according toclaim 1, consisting in adding the said leuco compound after productionof the sensitized emulsion and prior to development by impregnation.

15. A method of producing colored photographic images, according toclaim 1, consisting in adding the said leuco compound after produc tionof the sensitized emulsion and following development by impregnation.

16. A method of producing colored photographic images, according toclaim 1, consisting infadding the said leuco compound afterprovjelopment by impression. f

-17 A. method of producinglcolored. photo- 'raphic images, "according'to c'laiml, consisting .jir'iadding the said leuco compound afterproduc; "tion of the sensitized emulsionand'fol1owing"iie -ve1'opmentbyimpression.

I18. A method of producing colored "photographic images, according toclaim 1, consisting inadding the said leuco compound after produc-.tion'of the sensitized emulsion and pricrto development by applicationthereof in the form of a coating.

19. A method of producing colored photographic images, according toclaim 1, consisting in adding the said leuco compound after produc tionof the sensitized emulsion and following development by applicationthereof in the form of a coating.

20. A method of producing colored photographic images, consisting inadding a durable leuco compound to a metallic salt emulsion, per- 150},.which are free of metallic deposit, and finally treating with asolution or a powerful oxidizm' g agen 22. A method of producing.multi-colored photographic images, consisting in adding to a durableleuco compound in the preliminary stages of a sensitized metallic saltemulsion, performing exposure, developing and fixing in the customarymanner, and then introducing the exposed, developed and fixed image intoa bath acting on the said compound and locally converting the saidcompound into the desired color at the points which arefree of metallicdeposit,

and finally treating with a solution of a powerful oxidizing agent.

BELA GASPAR.

